Multiple-layer cylinder head gasket with integral pressure sensor apparatus for measuring pressures within engine cylinders

ABSTRACT

A multi-layer steel (MLS) cylinder head gasket containing fully integrated pressure sensors includes first and second metal layers with inner facing surfaces, and a spacer layer interposed between the facing surfaces. Outer (non-facing) surfaces of the first and second metal layers each include an elastomeric seal coating; the inner surfaces of the layers each include a friction reducing coating. Combustion apertures extend fully between the outer surfaces of the gasket, and are adapted to circumscribe cylinder bores of an engine. The spacer layer includes protective slots positioned adjacent each of the combustion apertures. Each slot wall contains a pressure sensor in form of a strain gauge to measure deflection of the wall resulting from pressure changes within engine combustion chambers. The measured deflections are correlated to actual pressures within the chambers. In the protective slots, the strain gauges are not exposed to combustion gases that could otherwise foul the sensors.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates generally to apparatus embedded in and orapplied to gasket structures, and particularly to sensing apparatusapplied to combustion gaskets of internal combustion engines. Morespecifically, the invention relates to pressure sensing apparatus formeasuring pressure levels of combustion gases that are provided withinstructures of cylinder head combustion gaskets.

2. Description of the Prior Art

It is known to employ electronic sensors in gaskets for sealing betweenengine components including, for example, the block and cylinder head ofa multi-cylinder internal combustion engine. In one such case, thegasket comprises a sealing plate having several combustion chamberorifices, with combustion chamber sealing elements situated on the edgesof the sealing plate surrounding the combustion chamber orifices. Thegasket includes sensor elements for cylinder-specific detection ofsealing movements perpendicular to the plane of the sealing plate,caused by pressure changes in respective combustion chambers beingmeasured. All of the sensor elements are arranged outside of thecombustion chamber sealing elements, and can be piezoelectric andpiezoresistive, as well as glass fiber light guide-style sensors.

In another example, a gasket enclosed sensor system is employed formeasurement of combustion chamber parameters and delivery of signals topoints external of the engine. The gasket includes a combustion openingsubstantially surrounding a combustion chamber, and includes an accessopening extending from the combustion chamber to a point external of theengine. A metallic sensor terminal is positioned within the accessopening, and insulating material substantially surrounds the metallicsensor terminal.

In yet another example, a fluid sensor and associated circuitry are usedto indicate presence of oil flow in a multi-cylinder internal combustionengine. The oil sensor includes a heating element positioned within theoil line, directly in the oil flow path. A comparator measures the valueof signals from upstream and downstream heat sensors, and triggers aswitching circuit when the temperature at the sensors approach oneanother to indicate an adequate oil flow to the engine.

In still another example, a gasket formed in the shape of an exhaustflange includes a load sensor comprising a pressure sensitiveelectrically resistive material positioned between electrodes andconductors extending outwardly of the perimeter of the gasket. A sealprovided between first and second layers of the gasket, and about theload sensor, provides a seal for the electrodes, which are positioned ina cavity to protect the sensor from fluids.

SUMMARY OF THE INVENTION

The present invention is a multi-layer steel (MLS) cylinder head gasketcontaining at least one fully integrated pressure sensor. The gasketcomprises first and second steel metal layers having inner and outersurfaces, with their inner surfaces substantially facing one another. Athird metal layer acts as a spacer layer; the spacer layer is interposedbetween and contacts the inner surfaces of the first and second layers.In the described embodiment, the outer surfaces of the first and secondlayers include an elastomeric seal coating, while the inner surfaces ofthe first and second layers include a friction reducing coating.

The cylinder head gasket further includes combustion apertures thatextend through each of the three described layers, thus contiguouslybetween the outer surfaces of the first and second metal layers. Thecombustion apertures circumscribe the cylinder bores. The gasket alsoincludes pressure sensors, for example strain gauges that are providedwith protective slots formed in the spacer layer adjacent to but spacedfrom each of the combustion apertures. Once the gasket has beeninstalled between a cylinder head and engine block, the strain gaugesare adapted to measure deflection of a wall of each of the slotsresulting from pressure changes occurring within the combustionchambers. For this purpose, the measured strains are correlated topressure changes within the combustion chambers to generate anappropriate electric signal.

One particular advantage of the disclosed MLS gasket is that the straingauges are not directly exposed to combustion gases that might otherwisefoul the sensor. As disclosed, the sensor is adhesively contained on anarcuate wall of the described protective slot. Sensor wires are attachedto the strain gauges; the wires are carried in grooves formed into thespacer layer. For accommodating a plurality of cylinders, wires fromeach cylinder bore are bundled into a common groove of the spacer layer.In an alternately described embodiment, the spacer layer can extendbeyond the normal boundary of the gasket. Thus, the spacer layer may beextended radially outwardly of a conventional gasket component perimeterin environments where such extension may be useful or desirable.Finally, a converter may be employed to change optical signals intoelectrical signals for appropriate transmittal to a microprocessor of anengine control module, if for example an optical strain gauge isemployed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a spacer layer of one described embodiment ofan MLS cylinder head gasket that incorporates a pressure sensor systemin accordance with the present invention, each sensor defined by astrain gauge disposed on an arcuate wall of a slot within the layer.

FIGS. 2 through 4 are cross-sectional views of three describedalternative embodiments of a cylinder head gasket that incorporates thesensor system of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Referring initially to FIGS. 1 and 2, a first described embodiment of acylinder head gasket 10 incorporates integral pressure sensor apparatusadapted to measure pressures in a combustion chamber. The gasket 10 isshown fragmentarily, and includes a pair of exterior mirror image layers12 and 14, as well as a center spacer layer 16 interposed between thelayers 12 and 14. The described gasket 10 is a multi-layer steel (MLS)gasket, although this invention is not limited to so-called MLS gaskets;indeed, the material can be of a metal other than steel. The gasket 10also includes a plurality of spaced bolt apertures 18, as shown, forsecurement of the three layered structure of the gasket 10 into propersealing alignment with combustion bores (not shown) situated between acylinder head and an engine block (neither shown). The gasket 10includes a plurality of combustion bore apertures of which only twoapertures, 20 and 22, are shown in FIG. 1.

Referring now particularly to FIG. 1, the pressure sensing apparatus isnow described in detail. A first slot 30 and an identical second slot 32are shown positioned respectively adjacent combustion bore apertures 20and 22. Those skilled in the art will appreciate that the samearrangement is applied to other bores not shown in the fragmentaryrendition of the gasket 10 in FIG. 1. Each of the slots 30, 32 containsa wall 34, 36, respectively, that is spaced from but adjacent the edgesof combustion bores 20, 22. Adhesively attached to each of the walls 34,36 is a strain gauge 40, 42 that has its longitudinal orientationextending along a circumferential arc within the slot 30, 32. Theadhesive employed in the described embodiment is a high temperatureadhesive of the type employed in internal combustion engines.

Adhesively applied to each strain gauge 40, 42 is a sensor harness 50that is adapted to measure movement of strain gauge 40, 42, and totransmit the movement as a signal through the sensor harness 50 and intosensor wires 52,54, respectively. The sensor wires 52,54 are positionedin channels 38 that extend radially outwardly from the slots 30, 32, andthat intersect a channel 46 at the border or edge of the spacer layer16, as shown. The channels 38 and 46 may be formed by being machined,coined, or ground, etc. Finally, the invention contemplates that thechannels are formed entirely within the spacer layer 16, so that thepressure sensor apparatus described may be fully contained within thespacer layer 16.

Referring now particularly to FIGS. 2 through 4, those skilled in theart will note that three separate embodiments of the gasket 10 aredisplayed, and that FIGS. 2 through 4 do not display wiring harnessesnor channels (FIG. 1) for reasons of convenience. Referring initially toFIG. 2, it will be appreciated that the exterior mirror image layers 12and 14 contain a series of mated upper and lower embossments or halfbeads 26, 28 at one end, and upper and lower full beads 27 and 29 nearthe combustion bore 20. In FIG. 3, the layers 12′ and 14′ contain fullbeads 44 and 45 along an intermediate portion of the cross-section,while containing half beads 48 and 49 at the combustion bore aperture20′. The embodiment of FIG. 3 also includes a fourth layer 56 thatcontains a stopper foldover layer 24, which is shown as a stopperannulus (also 24) in FIG. 1.

The embodiment of FIG. 4 is somewhat similar to that of FIG. 2, withrespect to embossments of the exterior mirror image layers 12″ and 14″.Specifically, the embodiment of the gasket 10″ incorporates a pair ofhalf beads 58 and 60, that are analogous to the half beads 26 and 28 ofthe gasket 10 of FIG. 2. Moreover, the gasket 10″ also contains a pairof full beads 59 and 61 that are situated similarly to the full beads 27and 29 of the gasket 10. However, the gasket 10″ incorporates acombustion ring 62 separate from the spacer layer 16″. This singularring 62 is situated radially adjacent each combustion opening (shown at20″), and is thicker than the spacer layer 16″ (e.g. in the range of0.08-0.15 mm″ as compared to the spacer layer thickness of approximately2 mm) to thus provide a so-called stand over or stopper effect at thecombustion opening 20″ in the absence of an actual stopper (e.g. thefoldover stopper 24 of FIG. 3).

In the described embodiments, the exterior mirror image layers 12 and 14of each design are constructed of spring steel with mechanically dieformed embossments, i.e. the beads and half beads described. The mirrorimage layers are typically made of 301 stainless-steel and may be ofhalf hardness or full hardness temper. Alternatively, they may be formedof high-strength steel alloys. In each case, it is contemplated that theouter surface of the layers 12 and 14 are coated with an elastomer sealcoating such as one containing silicone or fluoroelastomer (e.g., FKM),as will be appreciated by those skilled in the art. On the other hand, afriction reducing coating is applied to the inner surfaces 13, 15 of thelayers 12, 14. To the extent that the surfaces 13, 15 face one anotherand thus are adapted to engage the spacer layer 16, the contact frictionforces of the inner surfaces of the gasket are designed so as not toimpede the strain generation at the strain gauge location. Frictionreducing coatings such as moly disulfide, polytetrafluoroethylene, orsilicone power coatings can be used on surfaces 13, 15 for this purpose.

Those skilled in the art will appreciate that the above descriptionillustrates that various design options may be suitable in a variety ofgasket constructions, depending on a particular engine in which anappropriate sealing effect is to be achieved. Thus, it is to beunderstood that the above description is intended to be illustrative andnot limiting. Many embodiments will be apparent to those of skill in theart upon reading the above description. For example, a gasket within thesensor elements and wires molded into the body of the gasket materialwould fall within the broader scope of this invention. Therefore, thescope of the invention should be determined, not with reference to theabove description, but instead with reference to the appended claims,along with the full scope of equivalents to which such claims areentitled.

What is claimed is:
 1. A multi-layer cylinder head gasket for sealingcombustion chambers of an engine, the gasket comprising: first andsecond metallic sealing layers, each of the sealing layers having innerand outer planar surfaces, wherein said inner planar surfacessubstantially face one another; a third metallic layer comprising aspacer layer interposed between said inner surfaces of said first andsecond layers; each of said three layers comprising at least onecombustion aperture, and wherein each of the layers is sandwichedtogether so that the combustion apertures are concentrically aligned,and extend contiguously through the gasket layers between the outersurfaces of said sealing layers to collectively define a gasketcombustion aperture adapted to circumscribe one of the combustionchambers of an engine; said spacer layer further comprising a secondopening spaced from but adjacent to said combustion aperture of thatlayer; wherein said opening is not in direct gaseous communication withsaid gasket combustion aperture; said spacer layer further comprising apressure sensing device attached to an interior wall of said secondopening, said pressure sensing device adapted to measure deformation ofsaid interior wall resulting from pressure changes occurring in thecombustion chamber; and a sensor connection harness and a sensorconnection wire integrally attached to said pressure sensing device andterminating at said sensor connection harness.
 2. The multi-layer gasketof claim 1 wherein said second opening of said spacer layer comprises aprotective opening defined by a slot that contains said wall.
 3. Themulti-layer gasket of claim 2, wherein said wall is an arcuate wall thatis spaced from the combustion bore aperture of said spacer layer.
 4. Themulti-layer gasket of claim 3, wherein said gasket comprises a pluralityof said cylinder bores, and wherein pressure sensing apparatus isprovided near each bore for transmittal of cylinder-specific pressurelevel data to a real-time engine management system for optimization ofengine performance parameters.
 5. The multi-layer gasket of claim 4,wherein said pressure sensing device comprises a strain gauge.
 6. Themulti-layer gasket of claim 1, wherein said sealing layers of saidgasket comprise at least one beaded layer and wherein said beaded layersare concentrically registered with each other in said respective sealinglayers.
 7. The multi-layer gasket of claim 6, wherein said spacer layercomprises a surface channel adapted to receive said sensor connectionwires.
 8. A multi-layer cylinder head gasket for sealing combustionchambers of an engine, the gasket comprising: first and second metallicsealing layers, each of the sealing layers having inner and outer planarsurfaces, wherein said inner planar surfaces substantially face oneanother; a third metallic layer comprising a spacer layer interposedbetween said inner surfaces of said first and second layers; each ofsaid three layers comprising at least one combustion aperture, andwherein each of the layers is sandwiched together so that the combustionapertures are concentrically aligned, and extend contiguously throughthe gasket layers between the outer surfaces of said sealing layers tocollectively define a gasket combustion bore aperture adapted tocircumscribe one of the combustion chambers of an engine; said spacerlayer further comprising a second opening spaced from but adjacent tosaid combustion bore aperture of that layer; wherein said opening is notin direct gaseous communication with said gasket combustion aperture;said spacer layer further comprising a pressure sensing device attachedto an interior wall of said second opening, said pressure sensing deviceadapted to measure deformation of said interior wall resulting frompressure changes occurring in the combustion chamber; a sensorconnection harness and a sensor connection wire integrally attached tosaid pressure sensing device and terminating at said sensor connectionharness; and wherein said first and second metallic sealing layerscomprise a pair of beaded layers, each bead positioned symmetrically onsaid respective beaded layers.
 9. The multi-layer gasket of claim 8wherein said second opening of said spacer layer comprises a protectiveopening defined by a slot that contains said interior wall.
 10. Themulti-layer gasket of claim 9, wherein said slot comprises an arcuatewall that is spaced from the combustion bore aperture of said spacerlayer.
 11. The multi-layer cylinder head gasket of claim 10, comprisinga plurality of said cylinder bore apertures spaced apart within saidgasket, each of said bore apertures being closely spaced from one ofsaid pressure sensing devices responsive to said pressure levels of saidcombustion gases within that bore aperture, wherein each sensor ispositioned on an arcuate wall of said respective slot.
 12. Themulti-layer cylinder head gasket of claim 11, wherein said wires arecontained within channels positioned in said spacer layer, wherein saidchannels are radially oriented away from said slots.
 13. The multi-layercylinder head gasket of claim 12, wherein said pressure sensing devicescomprise strain gauges.